In our search for an inbred Syrian hamster which may be more susceptible to BOP pancreas cancer induction than other types of hamsters we shall first determine the most effective dose of BOP in our BIO 15.16 carcinogen-susceptible strain (now under way). As soon as they will be available, animals of the BIO 14.6 inbred strain will be studied because a fine structural pancreatic anomaly (marked distortion of endoplasmic reticulum in exocrine cells and occasional islet cells) has been noted, implying possible metabolic anomalies. The pancreatic response of these animals to BOP will be compared with those of a carcinogen-resistant inbred strain BIO 1.5 and with those of a hybrid bred from two carcinogen-susceptible inbred strains.